Aeroflex-Plainview · Since t here is no response to a Broadcas t Command, the setting of this ... is transmission line effects on lossy transmission lines on propagating waveforms

Aeroflex-PlainviewMIL-STD-1553 Glossary

Aeroflex Microelectronic Solutions MIL-STD-1553 Glossary Release 1

A1553Military standard that establishes requirements for digital, command/response timedMisionmultiplexing techniques. In this handbook, 1553 is used as a generic name for MlL-STD-1553(USAF),MIL-STD-1553A, and MlL-STD-1553B. Where a specific revision is referenced, the revision suffix isadded, e.g., 1553B.

Address Programming The method by which an RT is made unique from all others.

Analog Front End of a TerminalThe analog front-end portion of a 1553B terminal consists of one or more channels, each of whichcontains an interface to translate the 1553B bus signal into a digital signal with voltage levelsappropriate for the remainder of the terminal. The fact that most terminals being designed today usepurchased hybrid or VLSI IC parts has gone far toward simplifying terminal design.

Aperiodic A treatment which renders nonconductive material receptive to electroless deposition

Applications SoftwareElectronic components, such as transistors, diodes, thyristors, etc., which can operate on an appliedelectrical signal so as to change its basic character; i.e., rectification, amplification, switching, etc.

Asynchronous OperationAn electrical element capable of modifying an input voltage in such a way as to achieve rectification,amplification, or switching action, e.g., transistors. Discrete devices such as diodes or transistors; orintegrated devices, such as analog or digital circuits in monolithic or hybrid form.

Avionics An element of a circuit in which an electrical input signal is converted into an output signal by thenonlinear voltage/current relationships of a semiconductor device (see Active Components).

Avionics Hot BenchA network containing active and passive elements.

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BBitContraction of binary digit—may be either zero or one. In information theory, a binary digit is equal toone binary decision or the designation of one of two possible values or states of anything used to storeor convey information.

Bit Rate The number of bits transmitted per unit time, usually, per second.

BLACKThe designation applied to all wirelines, components, equipment, and systems which handle onlyencrypted or unclassified signals, and areas in which no unencrypted or classified signals occur.

Broadcast Operation of a data bus system such that information transmitted by the bus controller using a uniquebroadcast address is addressed to all of the terminals connected to the data bus.

Broadcast Command Received BitThis bit is set by an RT that implements Broadcast Commands any time that a valid BroadcastCommand has been received. Since there is no response to a Broadcast Command, the setting of thisbit allows the Bus Controller to subsequently check that the command was received properly byissuing a ‘Transmit Status” or “Transmit Last Command” Mode Command.

Built-in Test (BIT)The capability of an LRU to perform some form of self-test.

BusIn this Glossary (unless noted in the text) bus refers to 1553 data bus, which is the part of the networkwhich is terminated in its characteristic impedance, and to which stubs are attached. See Data Bus.Bus controller. The terminal assigned the task of initiating information transfers on the data bus. Thereis one (and only one) BC on a 1553B bus (at any given time), and this terminal totally controls the flowof information on the bus. No other terminal may transmit anything on the bus except as instructed bythe BC.

Bus CouplerThe circuit which is used to couple signals between the main bus cable and transformer coupled stubcables. A single stub bus coupler consists of a transformer, two isolation resistors, and a shieldedenclosure. Multiple stub bus couplers are also commercially available.

Bus Interface Unit (BIU) FunctionThis term is generally interchangeably with “terminal,” as defined in 1553B: “The electronic modulenecessary to interface the data bus with the subsystem and the subsystem with the data bus.Terminals may exist as separate line replaceable units (LRUs) or be contained within the elements ofthe subsystem.

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Bus Interface Unit (BIU) HardwareThis term describes a particular set of hardware that performs the interface between the data bus andthe internal portion of an embedded or standalone remote terminal. As a minimum, it refers to thedigital decode and encode logic that expands to the complete analog-to-digital interface between thedata bus and the internal remote terminal electronics or the subsystem for embedded terminals..

Bus MonitorsThe terminal assigned the task of receiving bus traffic and extracting selected information to be used ata later time A Bus Monitor does not transmit status words or anything else on the bus. It may have noterminal address, and in fact, can receive information addressed to any (or all) terminals on the bus. Asdefined in section 4.4.4 of 1553B, a Bus Monitor may have an assigned terminal address, in whichcase it will act just like an RT for commands to that address. The two most common applications of BusMonitors are: 1. Instrumentation, for recording bus traffic from many or all terminals for off-lineanalysis. 2. Backup BC, to provide a terminal with enough information to become the BC on the bus ifcommanded to do so, either with a “Dynamic Bus Control” Mode Command or by some other method.

Busy BitAn RT that is functional but that cannot transfer data to or from the subsystem on command from theBus Controller is busy. An RT that is busy should set the “Busy” bit in its Status Word responses on thebus.

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CCharacteristic Impedance (Zo)The value of impedance which, if it terminates a transmission line, results in no reflection along theline. Zo is usually specified at a certain frequency (1.0 MHz in 1553B, paragraph 4.5.1.2). Zo isapproximately equal to the square root of L/C, where L = inductance and C = capacitance per unitlength of cable.

Clock Rate The signal from the 1553B bus is asynchronous with any clock in the terminal, since a Manchestercode is by its nature self-clocking. That is, all Manchester-encoded bits have a zero-crossing in themiddle, and it is to this zero-crossing time that the data is referenced.

Command/ResponseOperation of a data bus system such that remote terminals receive and transmit data only whencommanded to do so by the bus controller.

Communications ProtocolSee Protocol.

Compool (global/local) (communication pool)This is a JOVIAL language term used to declare or define data by name that will subsequently be setor used by program procedures. The JOVIAL compiler establishes locations in memory for compooldata. As such, it is the means of data communications, and the scope of the declaration can be limited,hence the restriction “local.”

Configuration The specific functional structure of a given integrated system consisting of physical interconnection(topology) and system control. See Architecture.

Controller See Bus Controller.

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DData This term is used in this handbook to denote the content (16 bits) of information transferred on the1553 data bus in one data word.

Data BusWhenever a data bus or bus is referenced in this handbook, it implies all the hardware, includingtwisted-shielded pair cables, isolation resistors, transformers, etc., required to provide a single datapath between the bus controller and all the associated remote terminals.

Data Bus ConnectorsThe two physically separate connectors provided on the RT interface to the data bus.

Data Bus InterfaceThe part of the digital interface which is concerned with transferring data. See Digital Interface.

Data Bus LoadingData bus loading is the percent utilization of the total information transfer capacity of a multiplexed databus.

Data LatencyData latency is the age of the data, or how long it has been since the data was measured or calculatedto the point where it is used.

Data Wrap-AroundMany RTs include a “data wrap-around” function, in which data words sent to the RT with a receivecommand are send back to the bus controller with a subsequent transmit command.

Digital InterfaceEmbedded, high speed interface to the subsystem used to transfer control, status information and datato and from the subsystem.

Digital SectionThe remainder of the terminal other than the analog front end.

Direct CoupledA method of connecting terminals to the 1553 data bus using only a wire splice. Dispersion. Dispersionis transmission line effects on lossy transmission lines on propagating waveforms. It is a result offrequency-dependent velocity and frequency dependent attenuation which distorts the propagatingwave.

DMA Interface DMA hardware and DMA-CPU protocol establish the means by which data may be transferred to andfrom memory without direct CPU intervention.

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Droop The transient exponential decay of voltage across an inductor (typically a transformer winding) due tovoltage drop across the output impedance of the source driving the inductor as the current in thewinding increases (proportionally to the integral in time of the voltage).

Dual-redundantUse of two twisted, shielded cable pairs and interfaces for the purpose of greater reliability. DynamicBus Control. The operation of a data bus system in which designated terminals are offered control ofthe data bus, i.e., they become a BC when the terminal offering control relinquishes control.

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EEmbedded Interface1553 interface circuitry housed within a subsystem.

Encryption DesignsEncryption techniques used by the data bus network and its associated terminals and processors toconvert RED data into BLACK data and to isolate multiple classification levels and compartments ofRED data. The specific encryption technique and system design must be approved by the governmentagency responsible for encryption certification.

Equipment SpecificationsSee Specifications.

Error ManagementGeneral term used to describe the detection of transient events that temporarily degrade bus timing orperformance and the step-by-step sequence to branch to alternate functions, procedures, orequipment use.

Event A single occurrence at a precise time.

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FFail-Safe Timer MlL-STD-1553B requires (4.4.1.3 of 1553B) that every RT or BC contain a hardware timer to preventany transmission on the bus longer than 800 us. Since no valid transmission is longer than 660 us,only a failure in the terminal could result in a transmission of 800 us or longer. The fail-safe timer isrequired to prevent such a failure from causing a continuous transmission on the bus and thusrendering it (the bus) unusable for other transmissions.

Fault ManagementGeneral term used to describe the detection of intermittent or permanent events that require changesto system structure or operation and the step-by-step sequence to branch to alternate functions,procedures, or equipment use.

Function The special work done by a subsystem or a software task.

Fundamental ImpedanceSee Characteristic Impedance.

Fundamental WaveformDefined in this glossary to be the original impinging waveform. The waveform that is transmitted.

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GGatewayA unit that passes data between two data buses of similar bus type.

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HHalf DuplexOperation of a data transfer system in either direction over a single line, but not in both directions onthat line simultaneously.

Hierarchical ControlA form of distributing all system control in a system, where one level of control is subordinate to ahigher level of control.

Hierarchical NetworkA description of a physical topology that has both global and local levels of data buses.

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IIllegal CommandsA valid command that is not implemented in the receiving RT.

Input Threshold AdjustmentSome receivers allow the input voltage thresholds to be adjusted. It may be desirable to adjust thevoltage thresholds to alter the noise performance for some special applications. Receivers aregenerally supplied with the input voltage threshold adjusted for optimum performance, and the range ofacceptable threshold values is not wide.

Input-Output (I/O)This term is used to describe both the function of hardware and software to receive and transmit dataand the physical hardware section that is the interface between a 1553 interface and subsystems of aremote terminal or bus controller.

InstrumentationThe purpose of the “Instrumentation” bit is to enable the differentiation of Status Words and CommandWords, which are otherwise differentiated only by their position in a message.

IntegrationIn this handbook, integration refers to the cooperative need for shared information and the means forachieving that cooperation.

Intersymbol Interference (ISI) The effect seen as a pulse in a string of pulses distorting subsequent pulses as a result of beingpassed through a network that has less bandwidth than the spectrum of the pulses.

ISIIntersymbol interference (ISI) is the effect seen where a waveform is distorted by passing it through anetwork which either has less bandwidth than the signal, or is dispersive.

Invalid CommandA command in which the command word fails to meet validation criteria.

Isolation ResistorsTerminals for direct-coupled stubs require two isolation resistors between the terminal output and thebus connection. Their function is to isolate the bus from a terminal that has shorted (i.e., a terminalthat, due to some failure, is presenting an abnormally low impedance to the bus).

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LLinked Lists In linked list message processing, each message points to the next message to be transmitted. Thismethod makes it easy to insert messages into the middle of a particular minor frame’s messagestream.

Lossy In the context of lossy transmission line, the term lossy acknowledges the fact that transmission linesdo not have infinite, bandwidth and contribute to frequency shaping of a propagating pulse above andbeyond ideal reflective effects.

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MMain BusSee Bus.

Major CycleA period of scheduled time during which all periodic transmissions and computations occur at leastonce. Major cycles are divided into subcycles called minor cycles.

Manchester-coded Format Encoding and DecodingEach channel of the digital section contains an encoder/decoder function that deals with the data on abit and single-word level. Its purpose is to change the data from its Manchester-coded format into theproper digital data format (typically 16-bit parallel) needed by the rest of the terminal (and vice-versa),and to perform error detection for word-level 1553B errors (e.g., bit count errors, Manchester codingerrors, etc.). There must be a separate decoder for each channel, but there may be only one encoder.

Message In 1553 terms, a message is a part of an information transfer format, such as 1 to 32 data words. Amessage may also refer to the entire transmission by both bus controller and responding remoteterminal, which includes not only the data words but the overhead. This second usage is morecorrectly called an information transfer format. Definition from 1553: “A single message is thetransmission of a command word, status word, and data words if they are specified. For the case of aremote terminal to remote terminal (RT to RT) transmission, the message shall include the twocommand words, the two status words and data words.”

Message StacksThe stack method is the simplest to implement and allows for the implementation of minor and majorframes by use of separate stacks for each minor frame. The subsystem processor simply reinitializesthe stack pointer to the appropriate stack each time the particular minor frame is to begin.

Minor Cycle A period of scheduled time during which the most frequently occurring periodic transmission orcomputation will occur, or a period scheduled for a frequently occurring transmission or computation.Multiple minor cycles may be required to achieve a major cycle. See Major Cycle.

Mode CodeA means by which the bus controller can communicate with the multipiex-bus-related hardware inorder to assist in the management of the information flow.

Mode CommandAn information transfer format with the subaddress/mode field in the command word set to indicatethat the next following field is a mode code. An RT that implements Mode Commands is required toknow that a Subaddress/Mode field in a Command Word equal to 00000 or 11111 defines a ModeCommand, and that, in this case, the Word Count field is to be treated as the Mode Code rather thanthe number of words.

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Modem Modulator/Demodulator. In this handbook, this term is used to mean the analog transceiver circuitryused to convert to digital form. It is also used (loosely) to denote a bus interface unit function.

Modulation The signaling method used to convey data on the data bus.

Multiple-message Terminals A multiple-message terminal is a processor or sequencer in its own right. This type of terminal onlymakes sense as a BC, although some multiple-message BCs are capable of being configured to act asRTs upon command from the subsystem or with a discrete signal. It is capable of chaining severalmessages together, maintaining a schedule of messages required on the bus, and initiating alltransfers at the required times and in the required sequence. In system terms, the multiple-messageBC would be programmed with a whole minor frame or even major frame at a time.

Multiplex ProtocolSee Protocol.

Multiplex System Topology Multiplex system topology is the network of the data bus terminals, the components that comprise thedata bus, and the physical arrangement of redundant elements (whether terminals, bus controllers, orbus cables, coupler, or terminators). It includes all terminals and data buses involved in integrating thedata buses into the vehicle.

Multiplexing The transmission of information from several signal sources through one communication system.

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NNetwork Some devices are protected against short circuits applied to their outputs. This could be used toprotect parts in debugging or breadboarding activities. Note that this is somewhat inherent in thedesign of a current-mode transmitter.

Noise Noise is mainly due to reflections from impedance discontinuities in the bus network. Another sourceof noise is electromagnetic interference (EMI) or coupling of signals into the cable from other parts ofthe system. Both of these types of noise are mostly higher in frequency than the 1553B fundamentalfrequency of 1 MHz. This noise and signal distortion can cause multiple zero-crossings to occur in a bittime (1 microsecond) and can also cause a large error in the time of a zero-crossing (a zero-crossingshift error). This could cause the word to be misinterpreted by the decoder. It is most likely that thedecoder would detect a Manchester error, which is a bit that does not have opposite values in the twohalves of the bit time. Also, if one bit is distorted sufficiently that it is decoded as valid but of the wrongvalue, the decoder detects this error with the parity bit. Experience has shown that there is little needfor filtering of low-frequency noise. Good performance of the terminal in the presence of noise on thebus depends on input filtering and the proper setting of the input voltage thresholds.

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OOutput Short Circuit ProtectionSome devices are protected against short circuits applied to their outputs. This could be used toprotect parts in debugging or breadboarding activities. Note that this is somewhat inherent in thedesign of a current-mode transmitter.

Output Voltage AdjustmentSome transmitters offer adjustable output voltage. This feature could be very useful in the design oftest equipment but is of limited usefulness otherwise. Over-temperature Shutdown. Some devicesinclude a temperature sensor that shuts down the transmitter if it gets too hot. This is to protect thepart from damage, so it is desirable. However, this feature increases the cost and may slightlydecrease the device reliability.

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PPartitioning The method used to divide a complex system or function into manageable size before allocating thesesmaller pieces to devices to perform the required job.

Periodic Event(s) recurring at specific time intervals. See Aperiodic.

Polling This is the method of communicating with multiple terminals within a system to determining informationtransfer priorities or servicing needs. RTs might be polled to determine whether they have aperiodic orhigh priority messages to transmit, state of health, or capability of accepting bus control.

Protocol The conventions imposed on serial data to ensure that the receiver correctly interprets the transmitteddata; also, the procedures used for initiating messages and responding to them.

Pulse Code Modulation (PCM) The form of modulation in which the modulation signal is sampled, quantized, and coded so that eachelement of information consists of different types or numbers of pulses and spaces.

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RReceiver Input Filtering A method of electroplating in which the parts are affixed to a rigid rack.

Receivers Photographs made of the interior of a sealed package by use of X-rays to expose the film.

RED Random access memory; a type of memory which offers access to storage locations within it bymeans of X and Y coordinates.

RedundancyCircuit failures which occur randomly with the overall failure rate for the sample population being nearlyconstant.

Redundant Data BusA network composed only of resistors and capacitors.

RED/BLACK Metals that readily form compounds.

Reflection CoefficientThe surface area of an integrated circuit or of a hybrid or PCB substrate. The surface area required fora component or element.

Remote Terminal (RT) A second bonding attempt after a bond has been removed or failed to bond on the first attempt.

Retrofitting A second bond made on top of a removed or damaged bond or a second bond made immediatelyadjacent to the first bond.

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S Sample ConsistencyRelates to the consistency of data in a message. Messages transmitted shall contain only mutuallyconsistent samples of information, (i.e. all parameters shall be of the same sample set).

Sensor The hardware and software required to perform a specific system function, such as inertialmeasurement, radar detection.

Service Request BitThe purpose of this bit is to inform the Bus Controller that the RT wants the Bus Controller to request aparticular message to be transmitted from the RT to the BC.

Single-message TerminalsA single-message terminal has enough capability to construct or process a complete message withoutany action by the subsystem. Subsystem action is required only at the beginning or end of themessage or in the event of an error. The subsystem is responsible for processing any errors andinterpreting the status word contents, to decide what the next message should be, and then issuing it.This type of terminal is typically used with a microprocessor-based subsystem; the messages to besent are all constructed by the subsystem processor and placed in defined memory locations (to beread by the terminal via direct memory access (DMA)) or written to registers in the terminal.

Single-word Terminals In a system with a single-word terminal, the subsystem must process each word in each messageindividually. That is, a single-word terminal requires subsystem intervention or action for every word.After all the words have been received, the subsystem processor must determine the validity of themessage and construct the proper response. The response must then be transferred to the terminaland transmitted one word at a time.

Specification A document prepared specifically to support procurement that clearly and accurately describes theessential technical requirements for purchased material. Also included are procedures necessary todetermine that the requirements have been met for the purchased material covered by the document.

Standard A military standard is a document that establishes engineering and technical requirements forprocesses, procedures, practices, and methods that have been adopted as standard.

Status Flags Specific one bit fields in the status word generated by the RT to indicate its status.

Stub The connection of a terminal to the main bus, usually kept as short as possible to minimize distortion.May be either director transformer coupled.

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Stub Coupling The method of coupling an RT to the bus. These are generally transformer coupled, but some Navyapplications require both transformer and direct coupled stubs (Notice 2).

Subsystem The subsystem is defined in 3.8 of 1553B as “The device or functional unit receiving data transferservice from the data bus.” The subsystem is considered to be the portion of the LRU (line replaceableunit—the entire item of electronics) other than the terminal. In other words, it is the hardwareinterfacing with the nonbus side of the terminal. See Sensor.

System Flag Bit A status word bit that indicates that there is some fault condition in the subsystem associated with theRT.

Synchronous Events occurring at specific time intervals. See Aperiodic.

SystemThe interacting assembly of hardware, software, data, personnel, and facilities capable of performing adesignated function with specified results.

System ArchitectureIncludes the externally visible parts of a multiplex system, the internal partitioning of multiplexinterfacing elements, and the hardware and software used for data transport and transport control. Amultiplex system architecture consists of two major parts: system topology and system control.

System Block Diagram A graphic presentation of the partitions among functions. The blocks may represent actual parts ormaybe schematic representations. In a real system functions may be partitioned among the parts usedto implement the design.

System Configuration A 1553 bus system includes a BC (and possibly one or more backup BCs), one or more RTs (up to amaximum of 31), and zero or more bus monitors (typically not more than one, but could be anynumber). The BC has control of the system. It initiates messages that transfer data to or from an RT orcontrol the operation of an RT. Each RT receives data sent to it by the BC, transmits to the BC or toanother RT the data requested by the BC, or performs the commanded control function. A bus monitorlistens to the traffic on the bus and extracts whatever information it has been programmed to extract.

System ControlThe part of the architecture that implements the dynamic functioning of the multiplex system. Systemcontrol methodology is used to implement the protocol required for data transfers, the rules used inachieving media control and the procedures for initialization or startup, normal data bus transferoperations (such as, time synchronization, data security and data integrity), system error and faultmanagement techniques, and bus control mechanization.

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TTEMPEST An unclassified short name referring to investigations and studies or compromising emanations. It issometimes used synonymously for the term “compromising emanations” (e.g. TEMPEST tests,TEMPEST inspections, TEMPEST control plan).

Terminal The electronic module necessay to interface the data bus with the subsystem and the subsystem withthe data bus. Terminals may exist as separate LRUs or be contained within the elements of thesubsystem. The unit connects to the end of a stub which may be a transmitter or receiver. Thisdefinition allows a terminal to be a totally separate LRU, a circuit card, or a small portion of a circuitcard; there is no restriction on the physical partitioning of the system. However, the current trend intechnology is for smaller size and fewer parts. A terminal is either a Bus Controller (BC), a RemoteTerminal (RT), or a Bus Monitor. Nothing in 1553B precludes a terminal from including the capability ofperforming the functions of more than one of these three types of terminals, but a terminal mayperform only one function at anyone time.

Terminal Flag BitThis bit indicates that there is some fault condition in the RT. Remember that the RT is only that portionof the LRU necessary to communicate with the 1553 bus.

Terminal Partitioning Terminals may have various proportions of their design in hardware, firmware, and software. Typically,an older design, simple terminal would be almost all hardware, while a newer design, complex terminalwould consist largely of software or firmware

Time Division Multiplexing (TDM)The transmission of information from several signal sources through one communication system withdifferent signal samples staggered in time to form a composite pulse train.

TopologyThe interconnectivity of the data bus(es) and their associated elements (terminals and controllers) toaccomplish the desired data path required by the integration.

Transceivers Receivers and transmitters are generally packaged together as transceivers.

Transformer Another major analog component is the isolation transformer. It turns out that, to meet the terminalcharacteristics that are specified in 1553B, especially the common-mode rejection ratio (CMRR)requirement, an isolation transformer is the most appropriate design choice. As in the case of thetransceiver, transformers are usually bought and not built. There are many available on the market thatare specifically designed to work with available transceivers to meet the requirements of 1553B.

Transformer CoupledA method of connecting a stub to the 1553 data bus that uses a transformer and isolation resistors.

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Transmitters The transmitter is the element in the terminal that outputs waveforms to the bus. It accepts as its inputthe digital signal from the encoder (typically differential TTL) and produces a signal on the 1553 busthat meets the requirements of 1553. It typically contains two drivers, one for each side of thedifferential 1553 bus. Each is designed to control the rise and fall times and the waveshape of theoutputs. A transmitter also typically contains an inhibit input by which it maybe disabled.

Twisted Shielded PairA twisted, shielded pair of wires is used to interconnect the elements of a network (transformers,resistors and connectors). It is the primary constituent of the network and is commonly referred to ascable.

Transmission Coefficient The ratio of the voltage wave transmitted beyond an impedance discontinuity over the incident voltagewave (referred to as CT in this document). It is the number between 0 and 2.

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WWaveform QualityA phrase which addresses the amount of distortion with which a waveform arrives at its destination.

Word A 1553 word is a sequence of 20 bit times consisting of a 3 bit-time sync, 16 bits of data, and 1 paritybit. This is the word as it is transmitted on the bus; 1553 terminals add the sync and parity beforetransmission and remove them during reception. Therefore, the nominal word size is 16 bits; mostsignificant bit first. There are three types of words: command, status, and data.

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Aeroflex-Plainview · Since t here is no response to a Broadcas t Command, the setting of this ... is transmission line effects on lossy transmission lines on propagating waveforms